1. Field of the Invention
The present invention relates to a control system for agricultural implements, and more particularly to a control system that takes into account delays in turning on and off functions of the agricultural implements due to implement latency.
2. Description of the Related Art
Agricultural implements are commonly used to perform various agricultural functions, such as tilling, planting, spraying, and fertilizing. As modern farming methods have become more competitive, it has become increasingly important that fields and agricultural products to be applied to the fields are used efficiently. To this end, agricultural functions applied to the fields, whether such agricultural function is tillage, seeding, or application of fertilizer or other chemicals, are carefully controlled in order to prevent gaps where the agricultural function is not applied, or overlaps where the agricultural function is applied more than once.
In order to prevent this from happening, today's in-cab control systems accomplish overlap control using a centralized control system that commands an implement to “turn on now” or “turn off now” as the implement crosses a computed boundary, such as a boundary where the agricultural function has been performed before, or an edge boundary of the field. Such in-cab control systems use reactive models, so that the command is given when the boundary is crossed. Normally such systems are tied to GPS position information that is updated at a rate of 5 to 10 hertz, or 0.1 to 0.2 seconds between updates. At a typical sprayer speed of 25 miles per hour, for example, this can result in gaps or over-applications of 3½ to 7 feet. Further latency due to delays in software comparing the implement position to the boundary position, issuance of a command to the implement, and reaction to the command by the implement, particularly when the agricultural function has an inherent lag between actuators on the implement taking action and initiation or cessation of the agricultural function, can increase resultant gaps or over-applications considerably. Multiplied by the number of times that such boundaries are crossed in treating a given field, for example boundaries between rows and headland passes, these gaps or over-applications can add up to considerable wasted space or wasted agricultural resources.
In order to compensate for this, prior art systems have provided an operator the ability to program in a “start early” distance, a “stop late” distance, and a “product delay” time. The product delay represents the time between the system starting or stopping the agricultural implement and actual initiation or cessation of the agricultural function. Effectively, setting the product delay results in an offset of the reported location of the agricultural implement in the direction of travel of the agricultural implement. This new offset location is referred to as the product delay edge. The “start early” distance allowed for a further offset of the reported location of the agricultural implement in the direction of travel of the agricultural implement when transitioning from an overlap to a non-overlap area, i.e.—offset of the location of the agricultural implement toward the non-overlap area. This new offset location is referred to as the start early edge. The start early edge is used when initiating the agricultural function of the agricultural implement upon leaving the overlap area. The “stop late” distance allowed for a further offset of the reported location of the agricultural implement in the opposite direction to the direction of travel of the agricultural implement when transitioning from a non-overlap area to an overlap area, i.e.—offset of the location of the agricultural implement away from the overlap area. This new offset location is referred to as the stop late edge. The stop late edge is used when ceasing the agricultural function of the agricultural implement upon entering the overlap area. The “start early” and “stop late” distances allowed for fine-tuning of the performance of the agricultural implement after configuring the “product delay”.
As each of the “start early” distance, “stop late” distance, and “product delay” time resulted in an offset of the reported location of the agricultural implement, the prior art systems still relied upon a “turn on now” or “turn off now” command sent to the agricultural implement when the reported location of the agricultural implement intercepted a boundary between a non-overlap area and an overlap area, or vice versa. Actual initiation or cessation of the agricultural function is still subject to variation as a result of changes in vehicle speed, vehicle heading, variations in central control system latency, and GPS position update frequency. As noted previously, the GPS position update frequency in particular can account for as much as 7 feet of variation, even with the reported location of the agricultural implement offset to compensate for system latency. Furthermore, in a centralized control system, multiple individual latencies of various agricultural implements had to be accounted for by reprogramming the “product delay” time to compensate.
What is needed in the art is a control model for preventing or minimizing gaps or over-applications of agricultural functions by agricultural implements, while not relying upon the rate at which GPS position information is updated, not being dependent upon latency due to delays in software, and taking into account the individual latency in the reaction times of various agricultural implements.